Photoconductivity and photomemory in ZnXCd1–XIn2S4 layered crystals

Deep acceptor levels related to the ionization states of a double negatively charged center, A^2?, which cause high sensitivity in Zn_XCd_1–XIn₂S₄ layered crystals grown by chemical vapor deposition, have been investigated. The energy location, the capture cross section ratio and its dependence on the temperature have been determined by photoconductivity and thermal quenching experiments. The origin of a higher sensitivity and a region for the charge storage effect extending toward room temperature has been analyzed in crystals grown at the limit of existence of the quaternary layered phase. A possible origin of such centers due to zinc vacancy whose density increases with the partial substitution of cadmium by zinc atoms has been assumed to prove theoretical predictions and experimental results.